// SPDX-License-Identifier: MIT

#include <linux/export.h>
#include <linux/moduleparam.h>
#include <linux/vmalloc.h>

#include <drm/drm_crtc_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem.h>
#include <drm/drm_print.h>

#include <drm/drm_fbdev_ttm.h>

/* @user: 1=userspace, 0=fbcon */
static int drm_fbdev_ttm_fb_open(struct fb_info *info, int user)
{
        struct drm_fb_helper *fb_helper = info->par;

        /* No need to take a ref for fbcon because it unbinds on unregister */
        if (user && !try_module_get(fb_helper->dev->driver->fops->owner))
                return -ENODEV;

        return 0;
}

static int drm_fbdev_ttm_fb_release(struct fb_info *info, int user)
{
        struct drm_fb_helper *fb_helper = info->par;

        if (user)
                module_put(fb_helper->dev->driver->fops->owner);

        return 0;
}

FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(drm_fbdev_ttm,
                                   drm_fb_helper_damage_range,
                                   drm_fb_helper_damage_area);

static void drm_fbdev_ttm_fb_destroy(struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;
        void *shadow = info->screen_buffer;

        if (!fb_helper->dev)
                return;

        fb_deferred_io_cleanup(info);
        drm_fb_helper_fini(fb_helper);
        vfree(shadow);
        drm_client_buffer_delete(fb_helper->buffer);

        drm_client_release(&fb_helper->client);
}

static const struct fb_ops drm_fbdev_ttm_fb_ops = {
        .owner          = THIS_MODULE,
        .fb_open        = drm_fbdev_ttm_fb_open,
        .fb_release     = drm_fbdev_ttm_fb_release,
        FB_DEFAULT_DEFERRED_OPS(drm_fbdev_ttm),
        DRM_FB_HELPER_DEFAULT_OPS,
        .fb_destroy     = drm_fbdev_ttm_fb_destroy,
};

static void drm_fbdev_ttm_damage_blit_real(struct drm_fb_helper *fb_helper,
                                           struct drm_clip_rect *clip,
                                           struct iosys_map *dst)
{
        struct drm_framebuffer *fb = fb_helper->fb;
        size_t offset = clip->y1 * fb->pitches[0];
        size_t len = clip->x2 - clip->x1;
        unsigned int y;
        void *src;

        switch (drm_format_info_bpp(fb->format, 0)) {
        case 1:
                offset += clip->x1 / 8;
                len = DIV_ROUND_UP(len + clip->x1 % 8, 8);
                break;
        case 2:
                offset += clip->x1 / 4;
                len = DIV_ROUND_UP(len + clip->x1 % 4, 4);
                break;
        case 4:
                offset += clip->x1 / 2;
                len = DIV_ROUND_UP(len + clip->x1 % 2, 2);
                break;
        default:
                offset += clip->x1 * fb->format->cpp[0];
                len *= fb->format->cpp[0];
                break;
        }

        src = fb_helper->info->screen_buffer + offset;
        iosys_map_incr(dst, offset); /* go to first pixel within clip rect */

        for (y = clip->y1; y < clip->y2; y++) {
                iosys_map_memcpy_to(dst, 0, src, len);
                iosys_map_incr(dst, fb->pitches[0]);
                src += fb->pitches[0];
        }
}

static int drm_fbdev_ttm_damage_blit(struct drm_fb_helper *fb_helper,
                                     struct drm_clip_rect *clip)
{
        struct drm_client_buffer *buffer = fb_helper->buffer;
        struct iosys_map map, dst;
        int ret;

        /*
         * We have to pin the client buffer to its current location while
         * flushing the shadow buffer. In the general case, concurrent
         * modesetting operations could try to move the buffer and would
         * fail. The modeset has to be serialized by acquiring the reservation
         * object of the underlying BO here.
         *
         * For fbdev emulation, we only have to protect against fbdev modeset
         * operations. Nothing else will involve the client buffer's BO. So it
         * is sufficient to acquire struct drm_fb_helper.lock here.
         */
        mutex_lock(&fb_helper->lock);

        ret = drm_client_buffer_vmap_local(buffer, &map);
        if (ret)
                goto out;

        dst = map;
        drm_fbdev_ttm_damage_blit_real(fb_helper, clip, &dst);

        drm_client_buffer_vunmap_local(buffer);

out:
        mutex_unlock(&fb_helper->lock);

        return ret;
}

static int drm_fbdev_ttm_helper_fb_dirty(struct drm_fb_helper *helper,
                                         struct drm_clip_rect *clip)
{
        struct drm_device *dev = helper->dev;
        int ret;

        /* Call damage handlers only if necessary */
        if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
                return 0;

        ret = drm_fbdev_ttm_damage_blit(helper, clip);
        if (drm_WARN_ONCE(dev, ret, "Damage blitter failed: ret=%d\n", ret))
                return ret;

        if (helper->fb->funcs->dirty) {
                ret = helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);
                if (drm_WARN_ONCE(dev, ret, "Dirty helper failed: ret=%d\n", ret))
                        return ret;
        }

        return 0;
}

static const struct drm_fb_helper_funcs drm_fbdev_ttm_helper_funcs = {
        .fb_dirty = drm_fbdev_ttm_helper_fb_dirty,
};

/*
 * struct drm_driver
 */

int drm_fbdev_ttm_driver_fbdev_probe(struct drm_fb_helper *fb_helper,
                                     struct drm_fb_helper_surface_size *sizes)
{
        struct drm_client_dev *client = &fb_helper->client;
        struct drm_device *dev = fb_helper->dev;
        struct fb_info *info = fb_helper->info;
        struct drm_client_buffer *buffer;
        size_t screen_size;
        void *screen_buffer;
        u32 format;
        int ret;

        drm_dbg_kms(dev, "surface width(%d), height(%d) and bpp(%d)\n",
                    sizes->surface_width, sizes->surface_height,
                    sizes->surface_bpp);

        format = drm_driver_legacy_fb_format(dev, sizes->surface_bpp,
                                             sizes->surface_depth);
        buffer = drm_client_buffer_create_dumb(client, sizes->surface_width,
                                               sizes->surface_height, format);
        if (IS_ERR(buffer))
                return PTR_ERR(buffer);

        fb_helper->funcs = &drm_fbdev_ttm_helper_funcs;
        fb_helper->buffer = buffer;
        fb_helper->fb = buffer->fb;

        screen_size = buffer->gem->size;
        screen_buffer = vzalloc(screen_size);
        if (!screen_buffer) {
                ret = -ENOMEM;
                goto err_drm_client_buffer_delete;
        }

        drm_fb_helper_fill_info(info, fb_helper, sizes);

        info->fbops = &drm_fbdev_ttm_fb_ops;

        /* screen */
        info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST;
        info->screen_buffer = screen_buffer;
        info->fix.smem_len = screen_size;

        /* deferred I/O */
        fb_helper->fbdefio.delay = HZ / 20;
        fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;

        info->fbdefio = &fb_helper->fbdefio;
        ret = fb_deferred_io_init(info);
        if (ret)
                goto err_vfree;

        return 0;

err_vfree:
        vfree(screen_buffer);
err_drm_client_buffer_delete:
        fb_helper->fb = NULL;
        fb_helper->buffer = NULL;
        drm_client_buffer_delete(buffer);
        return ret;
}
EXPORT_SYMBOL(drm_fbdev_ttm_driver_fbdev_probe);